The present invention relates to absorbent garments incorporating monolithic films. More particularly, the present invention relates to absorbent garments incorporating monolithic films having zoned breathability and methods of making the same.
Various types of garments are presently available for absorbing human discharge. Examples of these garments include baby diapers, feminine care products, incontinence garments and the like. Generally speaking, the basic structure of this class of garments requires a liquid pervious body-side liner, an absorbent pad containing one or more layers for receiving and absorbing the discharge, and a liquid impervious backing member for containing the discharge.
While some of these absorbent garments perform satisfactorily for their intended purpose, there remains the need to provide a more discrete absorbent garment that possesses improved comfort characteristics.
Heretofore, some absorbent garments for absorbing and containing human discharge have typically been uncomfortable. For example, such absorbent garments may comprise flat sheets folded up into a diaper-like configuration having a film material that serves as liquid impervious outer cover. However, such film material lacks breathability, causing the absorbent garments to be hot and uncomfortable. The skin becomes overly hydrated by the aqueous liquids (for example, perspiration) trapped against the skin by the non-breathable film, resulting in skin occlusion.
Thus, it becomes apparent that a need exists for an absorbent garment that improves the containment characteristics of the absorbent garment while still being comfortable to wear as well as promoting skin wellness and skin dryness.
Monolithic films are xe2x80x9cbreathablexe2x80x9d barriers in the sense that the film acts as a barrier to liquids and particulate matter but allows water vapor and air to pass therethrough. In addition, by achieving and maintaining high breathability it is possible to provide an article that is more comfortable to wear since the migration of water vapor through the fabric helps reduce and/or limit discomfort resulting from excess moisture trapped against the skin. Thus, such an article can potentially contribute to an overall improved skin wellness.
Accordingly, breathable films have become an important article of commerce, finding a wide variety of applications. For example, breathable films have been used as backing members or as part of outer covers for personal care products such as diapers, training pants, incontinence garments, feminine hygiene products and the like. In addition, microporous films have likewise found use in protective apparel and infection control products such as surgical gowns, surgical drapes, protective workwear, wound dressings and bandages. Often breathable films are utilized as a multilayer laminate. The breathable films can provide the desired barrier properties to the article while other materials laminated thereto can provide additional characteristics such as strength, abrasion resistance and/or good hand. For example, fibrous webs such as nonwoven fabrics allow the laminate to retain its breathability and can provide additional strength as well as an article having a cloth-like feel. Thus, breathable film laminates can be used in a variety of applications including, for example, those described above.
In addition, monolithic films that act as a barrier to bacteria and viruses can provide an article or garment that reduces the contamination of the surroundings and the spread of infections and illness caused by the bacteria and viruses.
Although the breathability provided by such films and/or laminates thereof is advantageous in many articles, there exist some situations where high breathability can be undesirable. For example, in absorbent personal care articles such as diapers or incontinence garments the breathable barrier and absorbent core generally work together to retain bodily fluids (aqueous liquids) discharged into the garment. However, when aqueous liquid is retained within the absorbent core significantly higher levels of water vapor begin to pass through the breathable barrier. The increased levels of water vapor passing through the outer cover can form condensate on the outer portion of the garment. The condensate is simply water but can be perceived by the wearer as leakage. In addition, the condensate can create a damp uncomfortable feel to the outer portion of the garment which is unpleasant for those handling the article.
It is believed that the skin wellness and/or improved comfort benefits of breathable outer covers are not achieved at areas directly adjacent the portion of the absorbent core retaining considerable amounts of liquid (e.g. typically those areas of the central or crotch region of the garment). Providing a breathable barrier which has less or limited breathability in such regions, while providing good breathability in the remaining regions, would provide a garment with excellent wearer comfort yet which limits the potential for outer cover dampness and odors. Thus, a breathable barrier that provides either zoned or controlled regional breathability is highly desirable.
Therefore, there exists a need for a breathable film having regions with varied levels of breathability. In addition, there exists a need for such films which retain the desired barrier properties and which are capable of lamination to additional materials. Further, there exists a need for methods of making such films and in particular methods of reliably obtaining the desired levels of breathability in distinct regions of a film.
Thus, it becomes apparent that a need exists for a breathable absorbent garment that exhibits desired absorbency and containment characteristics of the garments while improving comfort during use.
The present invention provides an improved breathable absorbent garment having improved comfort characteristics. The breathable absorbent garment of the invention provides an absorbent pad disposed between a breathable backing member (also referred to as a monolithic film) and a body-side liner. The breathable absorbent garment may also include an elasticized design that also facilitates the formation of the crotch section, as well as an effective seal between the garment and the wearer, whereby the garment is comfortable to wear.
The aforesaid needs are fulfilled and the problems experienced by those skilled in the art overcome by the monolithic film of present invention which, in one aspect, comprises a first breathable region having a thickness less than 100 xcexc and a WVTR of at least 800 g/m2/24 hours and a second region having a WVTR less than that of the first region wherein the WVTR of the second region is at least 15% less than the WVTR of the first region. The monolithic film has a hydrohead of at least about 50 mbar. The second region desirably has minimum dimensions of 5 cm by 5 cm and still more desirably comprises from about 5% to about 75% of the area of said monolithic film. In a further aspect, the first region can have a WVTR in excess of about 2500 g/m2/24 hours and the second region a WVTR less than about 1500 g/m2/24 hours.
Additionally and/or alternatively, the second region can have a WVTR at least about 50% less than the WVTR of the first region. Further, the monolithic film can comprise a third region having a WVTR intermediate to that of the first and second regions. Still further, the monolithic film can comprise primarily of a thermoplastic polymer and in a further aspect, can comprise a thermoplastic polymer and other components as desired. One aspect of the present invention is to provide a monolithic film having zoned breathability. Such a monolithic film reduces, and in some cases, prevents condensation on the outer surface of the breathable absorbent garment.
Further aspects of the present invention will appear in the description hereinafter.
The term xe2x80x9cmonolithicxe2x80x9d is used herein to mean xe2x80x9cnon-porousxe2x80x9d, therefore a monolithic film is a non-porous film. Rather than holes produced by a physical processing of the monolithic film, the film has passages with cross-sectional sizes on a molecular scale formed by a polymerization process. The passages serve as conduits by which water (or other liquid) molecules can disseminate through the film. Vapor transmission occurs through a monolithic film as a result of a concentration gradient across the monolithic film. This process is referred to as activated diffusion. As water (or other liquid) evaporates on the body side of the film, the concentration of water vapor increases. The water vapor condenses and solubilizes on the surface of the body side of the film. As a liquid, the water molecules dissolve into the film. The water molecules then diffuse through the monolithic film and re-evaporate into the air on the side having a lower water vapor concentration.
As used herein the term xe2x80x9cnonwovenxe2x80x9d fabric or web means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable manner as in a knitted or woven fabric. Nonwoven fabrics or webs have been formed by many processes such as for example, meltblowing processes, spunbonding processes, hydroentangling, air-laid and bonded carded web processes.
As used herein the term xe2x80x9cspunbond fibersxe2x80x9d refers to small diameter fibers of molecularly oriented polymeric material. Spunbond fibers may be formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced as by, for example, in U.S. Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartman, U.S. Pat. No. 3,542,615 to Dobo et al, U.S. Pat. No. 5,382,400 to Pike et al., and U.S. Pat. No. 5,759,926 to Pike et al. Spunbond fibers are generally not tacky when they are deposited onto a collecting surface and are generally continuous.
As used herein the term xe2x80x9cmeltblown fibersxe2x80x9d means fibers of polymeric material which are generally formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually hot, gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter. Thereafter, the meltblown fibers can be carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin et al. Meltblown fibers may be continuous or discontinuous, are generally smaller than 10 microns in average diameter, and are generally tacky when deposited onto a collecting surface.
As used herein xe2x80x9cmultilayer nonwoven laminatexe2x80x9d means a laminate of two or more nonwoven layers such as, for example, wherein some of the layers are spunbond and some meltblown such as a spunbond/meltblown/spunbond (SMS) laminate. Examples of multilayer nonwoven laminates are disclosed in U.S. Pat. No. 4,041,203 to Brock et al., U.S. Pat. No. 5,178,931 to Perkins et al. and U.S. Pat. No. 5,188,885 to Timmons et al. Such a laminate may be made by sequentially depositing onto a moving forming belt first a spunbond fabric layer, then a meltblown fabric layer and last another spunbond layer and then bonding the laminate such as by thermal point bonding as described below. Alternatively, the fabric layers may be made individually, collected in rolls, and combined in a separate bonding step.
As used herein, the term xe2x80x9cmachine directionxe2x80x9d or xe2x80x9cMDxe2x80x9d means the length of a fabric or a product in the direction in which it is produced. The term xe2x80x9ccross machine directionxe2x80x9d or CD means the width of fabric or product, i.e. a direction generally perpendicular to the MD.
As used herein the term xe2x80x9cpolymerxe2x80x9d generally includes but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term xe2x80x9cpolymerxe2x80x9d includes all possible spatial configurations of the molecule. These configurations include, but are not limited to isotactic, syndiotactic and random symmetries.
As used herein, xe2x80x9cultrasonic bondingxe2x80x9d means a process performed, for example, by passing the fabric between a sonic horn and anvil roll as illustrated in U.S. Pat. No. 4,374,888 to Bornslaeger.
As used herein xe2x80x9cpoint bondingxe2x80x9d means bonding one or more layers of fabric at numerous small, discrete bond points. For example, thermal point bonding generally involves passing one or more layers to be bonded between heated rolls such as, for example an engraved pattern roll and a smooth calender roll. The engraved roll is patterned in some way so that the entire fabric is not bonded over its entire surface, and the anvil roll is usually flat. As a result, various patterns for engraved rolls have been developed for functional as well as aesthetic reasons. One example of a pattern has points and is the Hansen Pennings or xe2x80x9cHandPxe2x80x9d pattern with about a 30% bond area when new and with about 200 bonds/square inch as taught in U.S. Pat. No. 3,855,046 to Hansen et al.
As used herein, the term xe2x80x9cbarrierxe2x80x9d means a film, laminate or other fabric which is relatively impervious to the transmission of liquids and which has a hydrohead of at least about 50 mbar. Hydrohead as used herein refers to a measure of the liquid barrier properties of a fabric measured in millibars (mbar) as described herein below. However, it should be noted that in many applications of barrier fabrics, it may be desirable that they have a hydrohead value greater than about 80 mbar, 150 mbar or even 200 mbar.
As used herein, the term xe2x80x9cbreathabilityxe2x80x9d refers to the water vapor transmission rate (WVTR) of an area of fabric which is measured in grams of water per square meter per day (g/m2/24 hours). The WVTR of a fabric is the water vapor transmission rate which, in one aspect, gives an indication of how comfortable a fabric would be to wear. WVTR can be measured as indicated below and the results are reported in grams/square meter/24 hours.
As used herein the term xe2x80x9cbacksheetxe2x80x9d or xe2x80x9cbacking memberxe2x80x9d refers to the aqueous liquid impervious protective layer on the garment side of a personal care product which prevents bodily exudates from escaping from the product.
As used herein the term xe2x80x9cmonocomponentxe2x80x9d fiber refers to a fiber formed from one or more extruders using only one polymer. This is not meant to exclude fibers formed from one polymer to which additives have been added. As used herein the term xe2x80x9cmulticomponent fibersxe2x80x9d refers to fibers which have been formed from at least two polymers extruded from separate extruders but spun together to form one fiber. Multicomponent fibers are also sometimes referred to as conjugate or bicomponent fibers. The polymers of a multicomponent fiber are arranged in substantially constantly positioned distinct zones across the cross-section of the fiber and extend continuously along the length of the fiber. The configuration of such a fiber may be, for example, a sheath/core arrangement wherein one polymer is surrounded by another or may be a side by side arrangement, a pie arrangement or an xe2x80x9cislands-in-the-seaxe2x80x9d type arrangement. Multicomponent fibers are taught in U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 4,795,668 to Krueger et al. and U.S. Pat. No. 5,336,552 to Strack et al. Conjugate fibers and methods of making them are also taught in U.S. Pat. No. 5,382,400 to Pike et al. and may be used to produce crimp in the fibers by using the differential crystallization properties of the two (or more) polymers. The fibers may also have various shapes such as those described in U.S. Pat. No. 5,277,976to Hogle et al., U.S. Pat. Nos. 5,466,410 to Hills and 5,069,970 and 5,057,368 to Largman et al.
As used herein the term xe2x80x9cblendxe2x80x9d means a mixture of two or more polymers while the term xe2x80x9calloyxe2x80x9d means a sub-class of blends wherein the components are immiscible but have been compatibilized.
As used herein the term xe2x80x9cbiconstituent fibersxe2x80x9d or xe2x80x9cmulticonstituentxe2x80x9d refers to fibers which have been formed from at least two polymers extruded from the same extruder as a blend. The term xe2x80x9cblendxe2x80x9d is defined above. Biconstituent fibers do not have the various polymer components arranged in relatively constantly positioned distinct zones across the cross-sectional area of the fiber and the various polymers are usually not continuous along the entire length of the fiber, instead usually forming fibrils or protofibrils which start and end at random. Bicomponent and biconstituent fibers are discussed in U.S. Pat. No. 5,294,482 to Gessner and in the textbook Polymer Blends and Composites by John A. Manson and Leslie H. Sperling, copyright 1976 by Plenum Press, a division of Plenum Publishing Corporation of New York, ISBN 0-306-30831-2, at pages 273 through 277.
As used herein, the term xe2x80x9cscrimxe2x80x9d means a lightweight fabric used as a backing material. Scrims are often used as the base fabric for coated or laminated products.
As used herein, the term xe2x80x9cgarmentxe2x80x9d means the same as the term xe2x80x9cpersonal care productxe2x80x9d.
As used herein, the term xe2x80x9cinfection control productxe2x80x9d means medically oriented items such as surgical gowns and drapes, face masks, head coverings like bouffant caps, surgical caps and hoods, footwear like shoe coverings, boot covers and slippers, wound dressings, bandages, sterilization wraps, wipers, garments like lab coats, coveralls, aprons and jackets, patient bedding, stretcher and bassinet sheets and the like.
As used herein, the term xe2x80x9cpersonal care productxe2x80x9d means personal hygiene oriented items such as diapers, training pants, absorbent underpants, adult incontinence products, feminine hygiene products, and the like.
As used herein the term xe2x80x9cbacksheetxe2x80x9d refers to the aqueous liquid impervious protective layer on the garment side of a personal care product which prevents bodily exudates from escaping from the product.
As used herein, the term xe2x80x9cprotective coverxe2x80x9d means a cover for vehicles such as cars, trucks, boats, airplanes, motorcycles, bicycles, golf carts, etc., covers for equipment often left outdoors like grills, yard and garden equipment (mowers, roto-tillers, etc.) and lawn furniture, as well as floor coverings, table cloths, picnic area covers, tents and the like.